Тема 4. Properties of Engineering Materials

1. Memorize the following words:

external	зовнішній
load	навантаження
subject	підпадати, підлягати
constant	постійний
impact	тимчасовий
cause	спричиняти, викликати
compression	стискання
tensile	на розтяг
torsional	скручувальний, на скручування
shearing	зрізувальний, на зріз
bending	згинальний, на згинання
specimen	зразок
rupture	розрив
clamp	затискач
cross-section	поперечний переріз
ratio	коефіцієнт, співвідношення
penetration	проникнення
due to	завдяки
distortion	відхилення, деформація

2. Read and translate the text.

PROPERTIES OF ENGINEERING MATERIALS AND METHODS OF TESTING THEM

While using engineering materials in practice we must know their properties because they affect manufacture and application of materials. All engineering materials have definite characteristics determining their abilities to assume external loads because of which materials change their shape. When a metal is treated or when machine parts and tools are in the process of work the metals which they are made of are subjected to the influence of external forces. These forces are called “loads” and may have different characteristics: according to their value they may be small or large; according to the duration and character of their action they may be constant and impact. According to the influence of the loads upon the metal causing different changes of its shape, loads are distinguished as compression, tensile, torsional, shearing, and bending ones. By testing a metal under a load one can define what mechanical properties it has. In other words, one can determine strength, elasticity, plasticity, hardness and other properties of the metal. In order to have a clear conception of the metal properties it is subjected to tests on special devices and machines. The determination of these properties is made in the laboratory using a specimen from the metal to be tested. Let us consider some of the mechanical properties of metals, such as.

Strength of metals is the property of hard materials to be subjected to the influence of external forces without incurring damage and without changing their shape. The ultimate tensile strength of a material is that unit stress developed in the material by maximum slowly applied load that the material can resist without rupturing in a tensile test. A stress is the force within a body which resists deformation due to an externally applied load. If this load acts upon a surface of the unit area, it is called a “unit force”, and the stress resisting it is called a “unit stress”. An external force acting upon an elastic material, the material is deformed and the deformation is in proportion to the load. This distortion or deformation is called “strain”.

Special machines, called “rupture machines”, are used to test metals for strength. When testing a specimen, the upper clamp remains fixed and the lower one is being slowly lowered, thus causing the extension of the specimen. The load upon the specimen may be easily determined at any moment.

Elasticity is the ability of a material to change its shape under the influence of external loads and return to its original form upon removal of the loads. All materials are elastic but the range of elasticity varies for different materials. Elasticity is evaluated by means of the modulus of elasticity. The modulus of elasticity is the ratio of the unit stress S to the unit deformation Δl within the proportional limit of the material to be tested.

For determining the elasticity of metals a rupture machine may be used.

Plasticity is that property of a material when under the influence of loads, specimens of different materials may elongate while their cross-section decreases. Plasticity is the opposite of elasticity. So, plasticity is the ability of material to change its form without breaking under the influence of load and preserve this changed form after removal of the load. For determining the plasticity of metals a rupture machine may be used too.

Hardness of material is the property to resist deformation under applied load. Hardness is the most important mechanical property of metals. Hardness may also be defined as the ability of metals to resist penetration of other harder materials or as resistance to wear.

3. Answer the following questions.

1) Why is it necessary to know the properties of engineering materials?

2) How are the loads distinguished according to the influence upon the metal?

3) What are the most important mechanical properties of metals?

4) What is elasticity of metals?

5) What is plasticity of metals?

4. Memorize the following grammar material:

PRESENT CONTINUOUS TENSE

(Теперішній тривалий час)

+) Стверджувальна форма

I am	V1+ ing
he, she, it is	V1+ ing
we, you, they are	V1+ing

–) заперечна форма

I am not	V1+ ing
he, she, it is not	V1+ ing
we, you, they are not	V1+ ing

?) питальна форма

…am	I	V1+ ing
… is	he, she, it	V1+ ing
… are	we, you, they	V1+ ing

Цей час означає теперішню дію, яка відбувається зараз, або навколо теперішнього моменту, а також майбутню плановану дію. Вживається зі словами: зараз – now, у цей момент – at this moment, дивись – look, слухай – listen.

For example: I am working now. She is not going to the University at this moment. What is he writing now? They are going to their friends this evening.

Примітка. Існує група дієслів, які не вживаються в часах Continuous. До них належать to be – бути, to see – бачити, to love – любити, to like – подобатись, to hate – ненавидіти, to want – хотіти, to wish, to desire – бажати, to hear – чути, to feel – відчувати, to notice – помічати, to know – знати, to understand – розуміти, to remember – пам’ятати, to forget – забувати, to believe – вірити, to recognize – впізнавати, to seem, to appear – здаватися, to contain – містити, to consist – складатися.

5. Open the brackets and put the verbs into the Past, Future, Present Simple or Present Continuous tense.

1) They (to invent) a new device next week. 2) He usually (to come) to the University at 8 a.m. 3) We (to be) in Kharkiv two days ago. 4) That company (to produce) many buses every year. 5) They (to speak) about our order now. 6) He (not to want) to go to the conference at the moment. 7) The engineer (to discuss) that problem with you now. 8) He (to spend) a fortnight in their foreign branch in Italy last month. 9) Some employees (to repair) this equipment three days ago. 10) Where you (to place) your order? 11) Who (to take) my file yesterday? 12) The manager (to appoint) a meeting now. 13) They (to choose) a cheaper car at this shop last week. 14) Who (to make) a decision about our trip to London? 15) Our secretary (not to phone) your manager now. 16) Where they (to be) last week? 17) You (to make) an order now. 18) They (not to discuss) anything at the moment. 19) He (to develop) a new program later. 20) I (to help) you in half an hour.

6. Translate the following sentences into English.

1) Boни виграють це змагання наступного разу. 2) Я не зрозумів матеріал минулого разу. 3) Вони замовляють цей пристрій зараз. 4) Директор забрав документи минулого разу. 5) Це електронне обладнання дуже дорого коштує.

6) Ми використовуємо подібні дані на кожному лабораторному занятті. 7) Вона не знає властивостей металів. 8) Наші колеги пропонують зараз якісне обладнання. 9) Ваш підрядчик телефонує вам зараз. 10) Цей електронний пристрій не працює. 11) Наша компанія отримає хороше замовлення. 12) Вони продадуть нове обладнання. 13) Що таке «деформація»? 14) Вони не розмістили замовлення минулого тижня. 15) Ми зараз переглядаємо електронну пошту. 16) Які властивості металів ви знаєте?

7. Are the underlined verbs right or wrong? Correct the verbs that are wrong. Use Present Continuous or Present Simple.

1) Water boils at 100 degrees celsius. 2) The water boils. Can you turn it off? 3) Look! The man tries to open the door of your car. 4) Can you hear those people? What do they talk about? 5) The moon goes round the earth. 6) I must go now. It gets late. 7) I usually go to work by car. 8) Hurry up! It’s time to leave. OK, I come. 9) I hear you’ve got a new job. How do you get on? 10) Let’s go out. It doesn’t rain now. 11) She is very good at languages. She is speaking four languages very well.